Capacitive sensing during non-display update times

ABSTRACT

Embodiments of the invention generally provide an input device with display screens that periodically update (refresh) the screen by selectively driving common electrodes corresponding to pixels in a display line. In general, the input devices drive each electrode until each display line (and each pixel) of a display frame is updated. In addition to updating the display, the input device may perform capacitive sensing using the display screen as a proximity sensing area. To do this, the input device may interleave periods of capacitive sensing between periods of updating the display based on a display frame. For example, the input device may update the first half of display lines of the display screen, pause display updating, perform capacitive sensing, and finish updating the rest of the display lines. Further still, the input device may use common electrodes for both updating the display and performing capacitive sensing.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of pending patent application Ser.No. 13/606,354, filed Sep. 7, 2012, which claims benefit of U.S.provisional patent application Ser. No. 61/532,042, filed Sep. 7, 2011entitled “CAPACITIVE SENSING DURING NON-DISPLAY UPDATE TIMES,” which areherein incorporated by reference in their entireties. This applicationis related to U.S. patent application Ser. No. 13/606,547 filed on thesame day as this application entitled “DISTRIBUTED BLANKING FOR TOUCHOPTIMIZATION” with inventors Jeffrey Lillie, John Childs, ChristopherLudden, Thomas Mackin, and Petr Shepelev, which is herein incorporatedby reference.

BACKGROUND OF THE INVENTION

Field of the Invention

Embodiments of the present invention generally relate to performingcapacitance sensing while updating a display, or more specifically, toperforming capacitance sensing when display updating is paused.

Description of Related Art

Input devices including proximity sensor devices (also commonly calledtouchpads or touch sensor devices) are widely used in a variety ofelectronic systems. A proximity sensor device typically includes asensing region, often demarked by a surface, in which the proximitysensor device determines the presence, location and/or motion of one ormore input objects. Proximity sensor devices may be used to provideinterfaces for the electronic system. For example, proximity sensordevices are often used as input devices for larger computing systems(such as opaque touchpads integrated in, or peripheral to, notebook ordesktop computers). Proximity sensor devices are also often used insmaller computing systems (such as touch screens integrated in cellularphones).

BRIEF SUMMARY OF THE INVENTION

Embodiments of the invention generally provide a processing system for adisplay device comprising an integrated capacitive sensing device. Theprocessing system includes a driver module comprising driver circuitrywhere the driver module coupled to a plurality of common electrodesconfigured to be driven for updating a plurality of display lines in adisplay screen of the display device and performing capacitive sensing.The driver module is configured to drive a first one of the commonelectrodes for updating a first one of the display lines during a firsttime period of a first display frame and drive a second one of thecommon electrodes for updating a second one of the display lines duringa second time period of the first display frame. The driver module isfurther configured to drive a first transmitter electrode for capacitivesensing during a third time period of the first display frame where thefirst transmitter electrode comprises at least one of the plurality ofcommon electrodes. Moreover, the third time period is at least as longas the first time period and occurs after the first time period andbefore the second time period. The processing system also includes areceiver module coupled to a plurality of receiver electrodes andconfigured to receive resulting signals while driving the firsttransmitter electrode during the third time period. The processingsystem includes a determination module configured to determinepositional information for an input object based on the resultingsignals.

Embodiments of the invention generally provide a method for operating adisplay device comprising an integrated capacitive sensing device. Themethod includes driving a first common electrode of a plurality ofcommon electrodes for updating, during a first time period, a firstdisplay line of a first display frame and driving a second commonelectrode of the plurality of common electrodes for updating, during asecond time period, a second display line of the first display frame.The method includes driving first transmitter electrode for capacitivesensing during a third time period of the first display frame. The firsttransmitter electrode comprises at least one of the plurality of commonelectrodes, and the third time period is at least as long as the firsttime period and occurs after the first time period and before the secondtime period. The method includes receiving resulting signals on aplurality of receiver electrodes while driving the first transmitterelectrode during the third time period and determining positionalinformation for an input object based on the resulting signals.

Embodiments of the invention may further provide a display device havingan integrated capacitive sensing device. The display device includes aplurality of common electrodes configured to be driven for updating aplurality of display lines of a display screen of the display device andperforming capacitive sensing and a plurality of receiver electrodes.The display device includes a processor coupled to the plurality ofcommon electrodes and to the plurality of receiver electrodes. Theprocessor is configured to drive a first one of the common electrodesfor updating, during a first time period of a first display frame, afirst one of the display lines and a second common electrode forupdating, during a second time period of the first display frame, asecond one of the display lines. The processor is configured to drivefirst transmitter electrode for capacitive sensing during a third timeperiod of the first display frame where the first transmitter electrodecomprise at least one of the plurality of common electrodes, and thethird time period being at least as long as the first time period andoccurring after the first time period and before the second time period.The processor is configured to receive resulting signals on at least oneof the plurality of receiver electrodes while driving the firsttransmitter electrode during the third time period and determinepositional information for an input object based on the resultingsignals.

BRIEF DESCRIPTION OF DRAWINGS

So that the manner in which the above recited features of the presentinvention can be understood in detail, a more particular description ofthe invention, briefly summarized above, may be had by reference toembodiments, some of which are illustrated in the appended drawings. Itis to be noted, however, that the appended drawings illustrate onlytypical embodiments of this invention and are therefore not to beconsidered limiting of its scope, for the invention may admit to otherequally effective embodiments.

FIG. 1 is a schematic block diagram of an exemplary input device,according to an embodiment described herein.

FIG. 2 illustrates a stack-up of a sensor assembly that may be used inthe input device to sense the input object, according to an embodimentdescribed herein.

FIG. 3 is a timing chart for processing a display frame with interleavedcapacitive sensing periods, according to one embodiment disclosedherein.

FIG. 4 is a timing diagram for interleaving a capacitive sensing periodinto a display frame update, according to one embodiment disclosedherein.

FIG. 5 is a timing chart for processing a display frame with interleavedcapacitive sensing periods, according to one embodiment disclosedherein.

FIG. 6 is a graph illustrating noise susceptibility when switchingbetween display updating and capacitive sensing, according to oneembodiment disclosed herein.

FIGS. 7A-7C are timing charts for processing a display frame withinterleaved capacitive sensing periods, according to embodimentsdisclosed herein.

FIG. 8 illustrates a method of interleaving periods of capacitancesensing with display updating, according to an embodiment disclosedherein.

FIG. 9 illustrates a system for communicating between an electronicsystem and an input device that interleaves capacitive sensing periodswith display updating periods, according to one embodiment disclosedherein.

To facilitate understanding, identical reference numerals have beenused, where possible, to designate identical elements that are common tothe figures. It is contemplated that elements disclosed in oneembodiment may be beneficially utilized on other embodiments withoutspecific recitation. The drawings referred to here should not beunderstood as being drawn to scale unless specifically noted. Also, thedrawings are often simplified and details or components omitted forclarity of presentation and explanation. The drawings and discussionserve to explain principles discussed below, where like designationsdenote like elements.

DETAILED DESCRIPTION

The following detailed description is merely exemplary in nature and isnot intended to limit the invention or the application and uses of theinvention. Furthermore, there is no intention to be bound by anyexpressed or implied theory presented in the preceding technical field,background, brief summary or the following detailed description.

Various embodiments of the present technology provide input devices andmethods for improving usability. Input devices with display screensperiodically update (refresh) the screen by selectively driving commonelectrodes corresponding to pixels in the screen's display lines. Ingeneral, the input devices drive each electrode until each display line(and each pixel) of a display frame is updated. As used herein, adisplay frame includes the necessary information for updating, at leastonce, a defined portion of the display lines in a display screen. Forexample, if the input device updates the display screen sixty times asecond, the input device receives sixty display frames which the inputdevice uses to update each display line sixty times. Moreover, a displayframe may not include all the display lines in the display screen. Forexample, only a portion of the display screen may be actively displayingan image, and thus, the display frames may contain only the data neededto update the display lines in the active portion.

In addition to updating the display, the input device may performcapacitive sensing using the display screen as a proximity sensing area.Moreover, the input device may interleave periods of capacitive sensingbetween periods of updating the display based on a display frame. Forexample, the input device may update the first half of the display linesof the display screen, pause display updating, perform capacitivesensing, and finish updating the rest of the display lines. In thismanner, the time period necessary for updating a screen based on asingle display frame includes one or more interleaved periods ofcapacitive sensing. Further still, the input device may use commonelectrodes for both updating the display and performing capacitivesensing.

In one embodiment, the periods of capacitive sensing may be at least aslong as the time period needed to update a single display line. Forexample, the input device may use one or more common electrodes toupdate a single display line. After the line is updated, but beforestarting on the next display line, the input device may use the samecommon electrodes for capacitive sensing for a similar amount of time.Performing capacitive sensing for a time period at least equal to thetime needed to update a display line may permit the input device to usecontiguous sensing cycles to measure a capacitance or a change incapacitance associated with one or more of the common electrodes. Thatis, the capacitance measurement can be obtained without interrupting thesensing cycles.

FIG. 1 is a block diagram of an exemplary input device 100, inaccordance with embodiments of the present technology. Althoughembodiments of the present disclosure may be utilized in an input device100 including a display device integrated with a sensing device, it iscontemplated that the invention may be embodied in display deviceswithout integrated sensing devices. The input device 100 may beconfigured to provide input to an electronic system 150. As used in thisdocument, the term “electronic system” (or “electronic device”) broadlyrefers to any system capable of electronically processing information.Some non-limiting examples of electronic systems 150 include personalcomputers of all sizes and shapes, such as desktop computers, laptopcomputers, netbook computers, tablets, web browsers, e-book readers, andpersonal digital assistants (PDAs). Additional example electronicsystems 150 include composite input devices, such as physical keyboardsthat include input device 100 and separate joysticks or key switches.Further example electronic systems 150 include peripherals such as datainput devices (including remote controls and mice), and data outputdevices (including display screens and printers). Other examples includeremote terminals, kiosks, and video game machines (e.g., video gameconsoles, portable gaming devices, and the like). Other examples includecommunication devices (including cellular phones, such as smart phones),and media devices (including recorders, editors, and players such astelevisions, set-top boxes, music players, digital photo frames, anddigital cameras). Additionally, the electronic system could be a host ora slave to the input device.

The input device 100 can be implemented as a physical part of theelectronic system 150, or can be physically separate from the electronicsystem 150. As appropriate, the input device 100 may communicate withparts of the electronic system using any one or more of the following:buses, networks, and other wired or wireless interconnections. Examplesinclude I²C, SPI, PS/2, Universal Serial Bus (USB), Bluetooth, RF, andIRDA.

In FIG. 1, the input device 100 is shown as a proximity sensor device(also often referred to as a “touchpad” or a “touch sensor device”)configured to sense input provided by one or more input objects 140 in asensing region 120. Example input objects include fingers and styli, asshown in FIG. 1.

Sensing region 120 encompasses any space above, around, in and/or nearthe input device 100 in which the input device 100 is able to detectuser input (e.g., user input provided by one or more input objects 140).The sizes, shapes, and locations of particular sensing regions may varywidely from embodiment to embodiment. In some embodiments, the sensingregion 120 extends from a surface of the input device 100 in one or moredirections into space until signal-to-noise ratios prevent sufficientlyaccurate object detection. The distance to which this sensing region 120extends in a particular direction, in various embodiments, may be on theorder of less than a millimeter, millimeters, centimeters, or more, andmay vary significantly with the type of sensing technology used and theaccuracy desired. Thus, some embodiments sense input that comprises nocontact with any surfaces of the input device 100, contact with an inputsurface (e.g. a touch surface) of the input device 100, contact with aninput surface of the input device 100 coupled with some amount ofapplied force or pressure, and/or a combination thereof. In variousembodiments, input surfaces may be provided by surfaces of casingswithin which the sensor electrodes reside, by face sheets applied overthe sensor electrodes or any casings, etc. In some embodiments, thesensing region 120 has a rectangular shape when projected onto an inputsurface of the input device 100.

The input device 100 may utilize any combination of sensor componentsand sensing technologies to detect user input in the sensing region 120.The input device 100 comprises one or more sensing elements 121 fordetecting user input. As several non-limiting examples, the input device100 may use capacitive, elastive, resistive, inductive, magneticacoustic, ultrasonic, and/or optical techniques.

Some implementations are configured to provide images that span one,two, three, or higher dimensional spaces. Some implementations areconfigured to provide projections of input along particular axes orplanes.

In some resistive implementations of the input device 100, a flexibleand conductive first layer is separated by one or more spacer elementsfrom a conductive second layer. During operation, one or more voltagegradients are created across the layers. Pressing the flexible firstlayer may deflect it sufficiently to create electrical contact betweenthe layers, resulting in voltage outputs reflective of the point(s) ofcontact between the layers. These voltage outputs may be used todetermine positional information.

In some inductive implementations of the input device 100, one or moresensing elements 121 pick up loop currents induced by a resonating coilor pair of coils. Some combination of the magnitude, phase, andfrequency of the currents may then be used to determine positionalinformation.

In some capacitive implementations of the input device 100, voltage orcurrent is applied to create an electric field. Nearby input objectscause changes in the electric field, and produce detectable changes incapacitive coupling that may be detected as changes in voltage, current,or the like.

Some capacitive implementations utilize arrays or other regular orirregular patterns of capacitive sensing elements 121 to create electricfields. In some capacitive implementations, separate sensing elements121 may be ohmically shorted together to form larger sensor electrodes.Some capacitive implementations utilize resistive sheets, which may beuniformly resistive.

Some capacitive implementations utilize “self capacitance” (or “absolutecapacitance”) sensing methods based on changes in the capacitivecoupling between sensor electrodes and an input object. In variousembodiments, an input object near the sensor electrodes alters theelectric field near the sensor electrodes, thus changing the measuredcapacitive coupling. In one implementation, an absolute capacitancesensing method operates by modulating sensor electrodes with respect toa reference voltage (e.g. system ground), and by detecting thecapacitive coupling between the sensor electrodes and input objects.

Some capacitive implementations utilize “mutual capacitance” (or“transcapacitance”) sensing methods based on changes in the capacitivecoupling between sensor electrodes. In various embodiments, an inputobject near the sensor electrodes alters the electric field between thesensor electrodes, thus changing the measured capacitive coupling. Inone implementation, a transcapacitive sensing method operates bydetecting the capacitive coupling between one or more transmitter sensorelectrodes (also “transmitter electrodes”) and one or more receiversensor electrodes (also “receiver electrodes”). Transmitter sensorelectrodes may be modulated relative to a reference voltage (e.g.,system ground) to transmit transmitter signals. Receiver sensorelectrodes may be held substantially constant relative to the referencevoltage to facilitate receipt of resulting signals. A resulting signalmay comprise effect(s) corresponding to one or more transmitter signals,and/or to one or more sources of environmental interference (e.g. otherelectromagnetic signals). Sensor electrodes may be dedicated transmitterelectrodes or receiver electrodes, or may be configured to both transmitand receive.

In FIG. 1, a processing system 110 is shown as part of the input device100. The processing system 110 is configured to operate the hardware ofthe input device 100 to detect input in the sensing region 120. Theprocessing system 110 comprises parts of or all of one or moreintegrated circuits (ICs) and/or other circuitry components. (Forexample, a processing system for a mutual capacitance sensor device maycomprise transmitter circuitry configured to transmit signals withtransmitter sensor electrodes, and/or receiver circuitry configured toreceive signals with receiver sensor electrodes). In some embodiments,the processing system 110 also comprises electronically-readableinstructions, such as firmware code, software code, and/or the like. Insome embodiments, components composing the processing system 110 arelocated together, such as near sensing element(s) of the input device100. In other embodiments, components of processing system 110 arephysically separate with one or more components close to sensingelement(s) of input device 100, and one or more components elsewhere.For example, the input device 100 may be a peripheral coupled to adesktop computer, and the processing system 110 may comprise softwareconfigured to run on a central processing unit of the desktop computerand one or more ICs (perhaps with associated firmware) separate from thecentral processing unit. As another example, the input device 100 may bephysically integrated in a phone, and the processing system 110 maycomprise circuits and firmware that are part of a main processor of thephone. In some embodiments, the processing system 110 is dedicated toimplementing the input device 100. In other embodiments, the processingsystem 110 also performs other functions, such as operating displayscreens, driving haptic actuators, etc.

The processing system 110 may be implemented as a set of modules thathandle different functions of the processing system 110. Each module maycomprise circuitry that is a part of the processing system 110,firmware, software, or a combination thereof. In various embodiments,different combinations of modules may be used. Example modules includehardware operation modules for operating hardware such as sensorelectrodes and display screens, data processing modules for processingdata such as sensor signals and positional information, and reportingmodules for reporting information. Further example modules includesensor operation modules configured to operate sensing element(s) todetect input, identification modules configured to identify gesturessuch as mode changing gestures, and mode changing modules for changingoperation modes.

In some embodiments, the processing system 110 responds to user input(or lack of user input) in the sensing region 120 directly by causingone or more actions. Example actions include changing operation modes,as well as GUI actions such as cursor movement, selection, menunavigation, and other functions. In some embodiments, the processingsystem 110 provides information about the input (or lack of input) tosome part of the electronic system (e.g. to a central processing systemof the electronic system that is separate from the processing system110, if such a separate central processing system exists). In someembodiments, some part of the electronic system processes informationreceived from the processing system 110 to act on user input, such as tofacilitate a full range of actions, including mode changing actions andGUI actions.

For example, in some embodiments, the processing system 110 operates thesensing element(s) of the input device 100 to produce electrical signalsindicative of input (or lack of input) in the sensing region 120. Theprocessing system 110 may perform any appropriate amount of processingon the electrical signals in producing the information provided to theelectronic system. For example, the processing system 110 may digitizeanalog electrical signals obtained from the sensor electrodes. Asanother example, the processing system 110 may perform filtering orother signal conditioning. As yet another example, the processing system110 may subtract or otherwise account for a baseline, such that theinformation reflects a difference between the electrical signals and thebaseline. As yet further examples, the processing system 110 maydetermine positional information, recognize inputs as commands,recognize handwriting, and the like.

“Positional information” as used herein broadly encompasses absoluteposition, relative position, velocity, acceleration, and other types ofspatial information. Exemplary “zero-dimensional” positional informationincludes near/far or contact/no contact information. Exemplary“one-dimensional” positional information includes positions along anaxis. Exemplary “two-dimensional” positional information includesmotions in a plane. Exemplary “three-dimensional” positional informationincludes instantaneous or average velocities in space. Further examplesinclude other representations of spatial information. Historical dataregarding one or more types of positional information may also bedetermined and/or stored, including, for example, historical data thattracks position, motion, or instantaneous velocity over time.

In some embodiments, the input device 100 is implemented with additionalinput components that are operated by the processing system 110 or bysome other processing system. These additional input components mayprovide redundant functionality for input in the sensing region 120, orsome other functionality. FIG. 1 shows buttons 130 near the sensingregion 120 that can be used to facilitate selection of items using theinput device 100. Other types of additional input components includesliders, balls, wheels, switches, and the like. Conversely, in someembodiments, the input device 100 may be implemented with no other inputcomponents.

In some embodiments, the input device 100 comprises a touch screeninterface, and the sensing region 120 overlaps at least part of anactive area of a display screen of the display device 101. For example,the input device 100 may comprise substantially transparent sensorelectrodes overlaying the display screen and provide a touch screeninterface for the associated electronic system. The display screen maybe any type of dynamic display capable of displaying a visual interfaceto a user, and may include any type of light emitting diode (LED),organic LED (OLED), cathode ray tube (CRT), liquid crystal display(LCD), plasma, electroluminescence (EL), or other display technology.The input device 100 and the display device 101 may share physicalelements. For example, some embodiments may utilize some of the sameelectrical components for displaying and sensing. As another example,the display device 101 may be operated in part or in total by theprocessing system 110.

It should be understood that while many embodiments of the presenttechnology are described in the context of a fully functioningapparatus, the mechanisms of the present technology are capable of beingdistributed as a program product (e.g., software) in a variety of forms.For example, the mechanisms of the present technology may be implementedand distributed as a software program on information bearing media thatare readable by electronic processors (e.g., non-transitorycomputer-readable and/or recordable/writable information bearing mediareadable by the processing system 110). Additionally, the embodiments ofthe present technology apply equally regardless of the particular typeof medium used to carry out the distribution. Examples ofnon-transitory, electronically readable media include various discs,memory sticks, memory cards, memory modules, and the like.Electronically readable media may be based on flash, optical, magnetic,holographic, or any other storage technology.

FIG. 2 shows a portion of an exemplary pattern of sensing elements 121configured to sense in a sensing region associated with the pattern,according to some embodiments. For clarity of illustration anddescription, FIG. 2 shows the sensing elements 121 in a pattern ofsimple rectangles, and does not show various components. This pattern ofsensing elements 121 comprises a first plurality of sensor electrodes160 (160-1, 160-2, 160-3, . . . 160-n), and a second plurality of sensorelectrodes 170 (170-1, 170-2, 170-3, . . . 170-n) disposed over theplurality of transmitter electrodes 160. In one embodiment, this patternof sensing elements 121 comprises a plurality of transmitter electrodes160 (160-1, 160-2, 160-3, . . . 160-n), and a plurality of receiverelectrodes 170 (170-1, 170-2, 170-3, . . . 170-n) disposed over theplurality of transmitter electrodes 160. In another embodiment, thefirst plurality of sensor electrodes may be configured to transmit andreceive and the second plurality of sensor electrodes may also beconfigured to transmit and receive.

Transmitter electrodes 160 and receiver electrodes 170 are typicallyohmically isolated from each other. That is, one or more insulatorsseparate transmitter electrodes 160 and receiver electrodes 170 andprevent them from electrically shorting to each other. In someembodiments, transmitter electrodes 160 and receiver electrodes 170 areseparated by insulative material disposed between them at cross-overareas; in such constructions, the transmitter electrodes 160 and/orreceiver electrodes 170 may be formed with jumpers connecting differentportions of the same electrode. In some embodiments, transmitterelectrodes 160 and receiver electrodes 170 are separated by one or morelayers of insulative material. In some other embodiments, transmitterelectrodes 160 and receiver electrodes 170 are separated by one or moresubstrates; for example, they may be disposed on opposite sides of thesame substrate, or on different substrates that are laminated together.

The areas of localized capacitive coupling between transmitterelectrodes 160 and receiver electrodes 170 may be termed “capacitivepixels.” The capacitive coupling between the transmitter electrodes 160and receiver electrodes 170 change with the proximity and motion ofinput objects in the sensing region associated with the transmitterelectrodes 160 and receiver electrodes 170.

In some embodiments, the sensor pattern is “scanned” to determine thesecapacitive couplings. That is, the transmitter electrodes 160 are drivento transmit transmitter signals. Transmitters may be operated such thatone transmitter electrode transmits at one time, or multiple transmitterelectrodes transmit at the same time. Where multiple transmitterelectrodes transmit simultaneously, these multiple transmitterelectrodes may transmit the same transmitter signal and effectivelyproduce an effectively larger transmitter electrode, or these multipletransmitter electrodes may transmit different transmitter signals. Forexample, multiple transmitter electrodes may transmit differenttransmitter signals according to one or more coding schemes that enabletheir combined effects on the resulting signals of receiver electrodes170 to be independently determined.

The receiver sensor electrodes 170 may be operated singly or multiply toacquire resulting signals. The resulting signals may be used todetermine measurements of the capacitive couplings at the capacitivepixels.

A set of measurements from the capacitive pixels form a “capacitiveimage” (also “capacitive frame”) representative of the capacitivecouplings at the pixels. Multiple capacitive images may be acquired overmultiple time periods, and differences between them used to deriveinformation about input in the sensing region. For example, successivecapacitive images acquired over successive periods of time can be usedto track the motion(s) of one or more input objects entering, exiting,and within the sensing region.

The background capacitance of a sensor device is the capacitive imageassociated with no input object in the sensing region. The backgroundcapacitance changes with the environment and operating conditions, andmay be estimated in various ways. For example, some embodiments take“baseline images” when no input object is determined to be in thesensing region, and use those baseline images as estimates of theirbackground capacitances.

Capacitive images can be adjusted for the background capacitance of thesensor device for more efficient processing. Some embodiments accomplishthis by “baselining” measurements of the capacitive couplings at thecapacitive pixels to produce a “baselined capacitive image.” That is,some embodiments compare the measurements forming a capacitance imagewith appropriate “baseline values” of a “baseline image” associated withthose pixels, and determine changes from that baseline image.

In some touch screen embodiments, transmitter electrodes 160 compriseone or more common electrodes (e.g., “V-com electrode” or source driveelectrode) used in updating the display of the display screen. Thesecommon electrodes may be disposed on an appropriate display screensubstrate. For example, the common electrodes may be disposed on the TFTglass in some display screens (e.g., In Plane Switching (IPS) or Plan toLine Switching (PLS)), on the bottom of the color filter glass of somedisplay screens (e.g., Patterned Vertical Alignment (PVA) orMulti-domain Vertical Alignment (MVA)), etc. In such embodiments, thecommon electrode can also be referred to as a “combination electrode”,since it performs multiple functions. In various embodiments, eachtransmitter electrode 160 comprises one or more common electrodes. Inother embodiments, at least two transmitter electrodes 160 may share atleast one common electrode.

In various touch screen embodiments, the “capacitive frame rate” (therate at which successive capacitive images are acquired) may be the sameor be different from that of the “display frame rate” (the rate at whichthe display image is updated, including refreshing the screen toredisplay the same image). In some embodiments where the two ratesdiffer, successive capacitive images are acquired at different displayupdating states, and the different display updating states may affectthe capacitive images that are acquired. That is, display updatingaffects, in particular, the background capacitive image. Thus, if afirst capacitive image is acquired when the display updating is at afirst state, and a second capacitive image is acquired when the displayupdating is at a second state, the first and second capacitive imagesmay differ due to differences in the background capacitive imageassociated with the display updating states, and not due to changes inthe sensing region. This is more likely where the capacitive sensing anddisplay updating electrodes are in close proximity to each other, orwhen they are shared (e.g. combination electrodes). In variousembodiments, the capacitive frame rate is an integer multiple of thedisplay frame rate. In other embodiments, the capacitive frame rate is afractional multiple of the display frame rate. In yet furtherembodiments, the capacitive frame rate may be any fraction or integer ofthe display frame rate.

For convenience of explanation, a capacitive image that is taken duringa particular display updating state is considered to be of a particularframe type. That is, a particular frame type is associated with amapping of a particular capacitive sensing sequence with a particulardisplay sequence. Thus, a first capacitive image taken during a firstdisplay updating state is considered to be of a first frame type, asecond capacitive image taken during a second display updating state isconsidered to be of a second frame type, a third capacitive image takenduring a first display updating state is considered to be of a thirdframe type, and so on. Where the relationship of display update stateand capacitive image acquisition is periodic, capacitive images acquiredcycle through the frame types and then repeats. In some embodiments,there may be “n” capacitive images for every display updating state.

Performing Capacitive Sensing Between Display Line Updates

FIG. 3 is a timing chart 300 for processing a display frame withinterleaved capacitive sensing periods, according to one embodimentdisclosed herein. Specifically, the timing chart 300 illustrates thedifferent time periods in a display frame. Time periods A-D and F-H eachrepresent the time used to update a single display line of a displayscreen in the input device. This display line update time is furtherdivided into a time period used to update the pixels 310 of the displayline and a buffer time 315 that occurs between each display line update305. The buffer time 315 may be also referred to as a horizontalblanking period 315. The driver module may use the horizontal blankingperiod 315 to, for example, retrieve data needed to update the nextdisplay line, drive a voltage onto the common electrode(s) correspondingto the display line, or allow signals to settle to reduce interferencewhen updating subsequent display lines. Nonetheless, the embodimentsdisclosed herein are not limited to an input device with a horizontalblanking period 315 and may be used in a system where there is no buffertime between the pixel update period 310 and the next display lineupdate 305. In various embodiments, the horizontal blanking time 315 isreduced in length such that it is substantially non-existent. In otherembodiments, the horizontal blanking time 315 is reduced in length suchthat it is no longer than the time needed to configure a commonelectrode to update a display line.

Moreover, the common electrodes 0-N may be driven for display updatingin any order. For example, the driver module may update a display lineat the top of the display screen, and in the subsequent display lineupdate 305, update a display line at the bottom of the screen. As aresult, the input device may sequentially drive two common electrodesthat are not located sequentially in the display screen. Further still,a display frame may not update each display line of the display screenif, for example, only a portion of the display screen is activelydisplaying information. Thus, the common electrodes 0-N in chart 300 mayrepresent only a portion of the common electrodes in the input device.

In one embodiment time period E represents the time for capacitivesensing, or a capacitive sensing period. Time period E maybe at least aslong as the time to update a single line of the display screen. Inanother embodiment, time period E is longer than the time to update asingle line of a display screen. Moreover, the input device may use thesame common electrodes used to update the pixels of the display screento drive transmitter signals. That is, the common electrodes may servedual purposes. During a display update period, a common electrodeupdates the pixels in the display, but during a capacitive sensingperiod, the common electrodes are used as transmitter electrodes.

In one embodiment, after updating display lines during time periods A-D,the driver module may pause display updating and use time period E toperform capacitive sensing. During this time period, the driver modulemay not update any of the pixels in the display screen. Additionally,the driver module may drive transmitter signals on at least oneelectrode transmitter electrode (e.g., at least one a common electrode)in the display screen. Based on the resulting signals received whichinclude effects corresponding to the transmitter signals, the inputdevice derives positional information of an input object proximate to asensing region of the device. In one embodiment, the input devicemeasures a change in capacitive coupling between the common electrodedriving the transmitter signal and a receiver electrode. This capacitivechange is then used to derive the positional information of an inputobject. Although the embodiments provided herein discuss using thecommon electrodes for transmitting the transmitter signals, in otherembodiments the common electrodes may be used as the receiver electrodesfor receiving a resulting signal instead of the electrodes that drivethe transmitter signal. For example, the input device may include aseparate set of electrodes that drive the transmitter signals thatgenerate the resulting signals on the common electrodes. Further still,in another embodiment, a first common electrode set may be configuredtransmit transmitter signals and a second common electrode set may beconfigured to receive resulting signals. In various embodiments, duringtime period E, a transmitter electrode may be driven for capacitivesensing, where the transmitter electrode is separate from the commonelectrodes.

In one embodiment, the driver module performs the capacitive sensingduring a plurality of consecutive horizontal blanking periods 315, forexample, during the horizontal blanking periods 315 for time periodsA-D. During each individual horizontal blanking period 315, only aportion of the information needed to acquire the capacitive measurementmay be captured. The horizontal blanking periods 315 may be too shortfor the input device to derive an accurate capacitive measurement for aparticular transmitting electrode. However, after a performingcapacitive sensing during a plurality of horizontal blanking periods315, the input device may derive an accurate measurement of the changein capacitive coupling for a selected electrode. Such a method ofcapacitive sensing during a horizontal blanking time 315 is referred toherein as non-contiguous capacitive sensing because the sensing cyclesfor obtaining the capacitive measurement for a particular electrode aretransmitted intermittently during each consecutive horizontal blankingperiod 315. Stated differently, non-contiguous capacitive sensing may bewhen capacitive sensing for a single electrode (or a group of selectedelectrodes) extends over two or more discontinuous time periods.

Alternatively or additionally, the driver module may pause updating thedisplay in order to perform capacitance sensing. As shown in chart 300,the driver module updates the pixels associated with common electrodes0-3 during time periods A-D. However, at time period E, display updatingis paused (i.e., the driver module does not continue to update the nextdisplay line in the frame) while capacitive sensing is performed.Specifically, the capacitive sensing periods 320 are interleaved withthe display line updates of the display frame. Accordingly, thecapacitive sensing period may also be referred to as an in-frameblanking period, a long horizontal blanking period, or a long h-blankperiod where display updating is paused while the driver module performscapacitive sensing. The driver module resumes display updating for thesame display frame after the capacitive sensing period 320 is finished.In one embodiment, the capacitive sensing periods 320 are longer thanthe horizontal blanking periods 315 and, in some embodiments, are atleast as long as the pixel update period 310 or the display line update305. While shown as being as long as display update period 305, invarious embodiments, the capacitive sensing period 320 may be longerthan a display update period 305. As shown, time period E is three timesas long (as shown by the horizontal and vertical arrows) as other timeperiods in chart 300—i.e., time periods A-D and F-H. However, theduration of the capacitive sensing periods 320 may be adjusted accordingto the particular design of the input device. In addition to performingcapacitive sensing during period 320, in one embodiment the drivermodule also performs capacitive sensing during one or more horizontalblanking periods 315 of the display line updates 305.

Allowing the capacitive sensing to occur during the capacitive sensingperiod 320 may allow the input device to measure accurately the changein capacitance for the selected electrodes (i.e., electrodes driving thetransmitter signal) without interruption or to improve interferencesusceptibility. Accordingly, performing capacitive sensing during ancapacitive sensing period 320 is referred to herein as contiguouscapacitive sensing since change in capacitive coupling is measured for aselected electrode or group of electrodes in a continuous time period.

Furthermore, the driver module may perform capacitive sensing using theelectrodes that were used in the previous display update period. Forexample, during time period E, the driver module may drive a transmittersignal simultaneously on common electrodes 0-3. In this manner, thedriver module may use one or more common electrodes to update the pixelsin a display line and, before continuing to update the other displaylines in the display frame, perform capacitive sensing using those sameelectrodes.

When display updating is paused, the driver module may still drivesignals on the common electrodes that are not driving the transmittersignal. For example, while the transmitter signal is transmitted on oneor more electrodes, the driver module may apply a reference voltage (oranother other signal) to other common electrodes in the display screen.Fixing the common electrodes currently not being used for capacitivesensing to a reference voltage may improve the ability of the inputdevice to derive accurate positional information for the input object.Thus, when display updating is paused, the driver module may cease toupdate the pixels in the display screen but still use the commonelectrodes for capacitive sensing.

The vertical blanking period 325 is the period between the last displayline update period of a display frame and the beginning of a row updateperiod in a subsequent display frame. Although not shown in FIG. 3, thetiming chart 300 may also include a second vertical blanking period atthe beginning of updating a display based on a received displayframe—i.e., before time period A. Because the input device does notupdate the display during these vertical blanking periods, in someembodiments, the driver module may also use either the first or thesecond vertical blanking periods (or both) to perform capacitancesensing. Similar to the capacitive sensing period 320, the verticalblanking periods 325 facilitate contiguous capacitive sensing since bothof these blanking periods may provide a sufficient length of time tomeasure the change in capacitance associated with a selected commonelectrode without significant interruptions. However, the verticalblanking period 325 is distinguished from the capacitive sensing period320 since this period 325 falls either at the beginning or end of thedisplay frame update while the capacitive sensing period 320 is insertedbetween display line updates of the same display frame.

In many embodiments, the length of a horizontal blanking period 315,capacitive sensing period 320 and/or a vertical blanking period 325 maybe changed. However, the display frame rate may not be able to bechanged. Therefore, as the length of one of these non-display updateperiods is changed, at least one of the other non-display update periodsmay also change. For example, in an embodiment where a capacitivesensing period 320 is included within the display frame, the duration ofthe horizontal blanking periods 315 and/or the vertical blanking period325 may be decreased correspondingly. By reducing the horizontalblanking periods 315 corresponding to the display line update periods305 of a first set of common electrodes, a capacitive sensing period 320may be inserted within a display frame. Given that a horizontal blankingperiod 315 is “T” μs long, reducing the horizontal blanking period 315to “N” μs for “M” corresponding common electrodes means an in-frameblanking period 320 of length “(T−N)*M” μs may be created. In oneembodiment, T−N may be reduced such that the horizontal blanking periods315 still provide enough time for the necessary display updateprocedures. The duration of a capacitive sensing period 320 may be basedon a sum of the reduction of each horizontal blanking period 315. Inother embodiments, the duration of the in-frame blanking period 315 maybe based on changing the vertical blanking period 325, or based onchanging both the horizontal blanking periods 315 and the verticalblanking period 325.

The duration of an capacitive sensing period 320 may be set accordingto, for example, the amount of time required to perform contiguouscapacitive sensing for a corresponding group of common electrodes, tomitigate noise from switching between capacitive sensing and displayupdating, or to perform frequency hopping or change in the capacitivesensing frame rate to reduce noise interference. For example, for agroup of common electrodes, 100 μs may be needed for contiguouscapacitive sensing. Therefore, a corresponding capacitive sensing period320 is determined to be at least 100 μs in length. To free up 100 μs butstill maintain the desired frame rate, one or more of the horizontalblanking periods 315 or the vertical blanking period 325 may be reduced.

Even though FIG. 3 was described in an embodiment where commonelectrodes 0-N are used for both updating a display and performingcapacitive sensing, this disclosure is not limited to such. In oneembodiment, the input device may use in-frame blanking periods toperform capacitive sensing even if the transmitter signals are driven onelectrodes that are not used when updating the display. Because theelectrodes used for display updating and the electrodes used forcapacitive sensing may be in close proximity in the input device,performing the two functions in mutually exclusive time periods mayreduce the amount of electrical interference between the differentelectrode sets.

FIG. 4 is a timing diagram for interleaving a capacitive sensing periodinto a display frame update, according to one embodiment disclosedherein. The timing diagram 400 includes the waveforms propagated oncommon electrodes 0-5 during the time periods A-F shown in FIG. 3.During time periods A-D, the driver module activates one of the commonelectrodes and updates the pixels associated with the correspondingdisplay line. While one electrode is activated, the other electrodes maybe kept at a constant voltage. Moreover, the common electrodes may notswitch instantaneously at each time period as shown (e.g., electrode 0switches off as electrode 1 switches on). Instead, there may be somedelay—e.g., the horizontal blanking period—where the electrodes ramp upor ramp down. In various embodiments, multiple common electrodes may bedriven in a delayed manner, where a first common electrode is activated,then after some delay, a second common electrode is driven.

During time period E, the driver module pauses display updating andswitches to capacitive sensing. In FIG. 4, one or more common electrodesare grouped into a transmitter electrode where the transmitter signal(e.g., the square wave) is transmitted simultaneously on each commonelectrode assigned to the transmitter electrode. For example, a displaydevice may include hundreds of common electrodes but, when performingcapacitance sensing, the device may segment the common electrodes intotransmitter electrodes (e.g., around 20 transmitter electrodes of 40common electrodes each) where each transmitter electrode is treated as asingle transmitter electrode. In another embodiment, the common voltageelectrode may be segmented into a plurality of common electrodes, wherea transmitter electrode comprises a single common electrode. Further, inother embodiments, the common voltage electrode may be segmented intoany number of common electrodes, where any number of common electrodesmay be combined to form a transmitter electrode. For simplicity, FIG. 4illustrates an embodiment where common electrodes 0-3 are assigned toone transmitter electrode and are each driven by the same transmittersignal. Alternatively, in other display devices, the common electrodesmay be a single electrode “plane” made up of a plurality of commonelectrode segments (common electrodes) are driven to a same referencevoltage during display updating. During capacitive sensing however, thedifferent common electrode segments (i.e., common electrodes) of theelectrode plane are used to transmit the transmitter signals atdifferent times, performing as one or more transmitter electrodes.

The capacitance sensing period may further be divided into a pluralityof sensing cycles 410 (or touch cycles). Advantageously, using anin-frame blanking period may permit the driver module to drive aplurality of contiguous sensing cycles sufficient for deriving a changein capacitance between the electrode block and one or more receiverelectrodes. For example, assuming the input device performs six sensingcycles 410 in order to accurately measure the change of capacitance butcan only perform two sensing cycles 410 during a horizontal blankingperiod 315, the driver module must use at least three horizontalblanking periods 315 for each electrode block. Conversely, with thein-frame blanking period 320 shown in FIG. 4, the input device measuresthe six sensing cycles 410 contiguously without updating the displaybetween the sensing cycles 410.

Of course, the input device may be configured to perform more or lessthan six cycles during a capacitive sensing period 320. Moreover, theinput device may perform capacitance sensing on multiple transmitterelectrodes during a single capacitive sensing period 320. For example,the driver module may drive the necessary sensing cycles 410 on commonelectrodes 0-3 and then drive the necessary sensing cycles on commonelectrodes 4-7. Further still, the driver module may also drive avoltage on the other common electrodes that are not used for capacitancesensing during the in-frame blank period 320. That is, instead ofpermitting the voltage on the other common electrodes (e.g., commonelectrode 4 and 5) to float, the driver module may drive a substantiallyconstant voltage (e.g., a reference voltage) on these electrodes.

In one embodiment, the input device transmits a transmitter signal onmultiple transmitter electrodes simultaneously during a capacitivesensing period 320. Although not shown, the driver module may output adifferent transmitter signal on each transmitter electrode based on amultiplexing schema such as code division multiplexing or orthogonalfrequency division multiplexing. Thus, the embodiments disclosed hereinare not limited to transmitting the same transmitter signal on a subsetof the common electrodes but may transmit different transmitter signalson a plurality of transmitter electrodes simultaneously in order tomeasure the change of capacitance between the transmitter electrodes andthe receiver electrodes.

FIG. 5 is a timing chart for processing a display frame with interleavedcapacitive sensing periods, according to one embodiment disclosedherein. In contrast to FIG. 3, timing chart 500 illustrates the timingfor updating a signal display frame with multiple capacitive sensingperiods 320. As used herein, a plurality of sequential display lineupdates are referred to as a display update cluster 505. Accordingly,referring to FIG. 3, the display line updates performed during timeperiods A-D may be described as a single display update cluster 505.Each display update cluster 505 (or capacitive sensing period) in adisplay frame update may be similar in duration or have differentdurations. Furthermore, the number of common electrodes in a displayupdate cluster 505 may be the same number of common electrodes used forcapacitance sensing in each capacitive sensing period 320 or the numberof electrodes used may be different.

FIG. 6 is a graph illustrating noise susceptibility when switchingbetween display updating and capacitive sensing, according to oneembodiment disclosed herein. The interference susceptibility of theinput device may be reduced by performing capacitive sensing during anin-frame blanking period. Capacitive sensing during the in-frameblanking period allows for the capacitive coupling between a block ofcommon electrodes and receiver electrodes to be determined in acontiguous manner. In one embodiment, the interference susceptibility isreduced in frequencies below those pertaining to the response of aninput object. Further, capacitive sensing during an in-frame updateperiod may provide a frequency response that has a wider lobe with fewerharmonics. In one embodiment, the main lobe is proximate to thefrequency response of an input object. FIG. 6 illustrates a comparisonbetween the frequency susceptibility of non-contiguous capacitivesensing and contiguous capacitive sensing. As shown, the frequencysusceptibility for non-contiguous capacitive sensing includes morepeaks, which may increase the interference susceptibility of the inputdevice near those peaks. For example, for low frequency, contiguouscapacitive sensing is substantially immune to lower frequencyinterference, while non-contiguous capacitive sensing may be susceptibleto such interference as illustrated by the lobes at 75 kHz, 140 kHz, and210 kHz. In one embodiment, an external power supply may introduce lowfrequency interference (e.g., below 200 kHz). In such an embodiment,transmitting signals for capacitive sensing with common electrodesduring an in-frame blanking period (contiguous capacitive sensing)reduces susceptibility to such interference.

In one embodiment, the input device may shift frequencies it uses totransmit the transmitter signals on the common electrodes. For example,the common electrodes are configured to transmit a first transmittersignal for capacitive sensing during in-frame blanking period, the firsttransmitter signal having a first transmitter frequency. In response tomeasuring interference at the first transmitter frequency, the drivemodule may drive a second transmitter signal having a second frequencydifferent from the first transmitter frequency on the common electrodes.The input device may compare the detected interference to one or morethresholds and switch from the first frequency to the second frequency(or back to the first frequency from the second frequency) when theinterference meets or exceeds one of the thresholds. Moreover, thesecond transmitter signal may include at least one of a differentamplitude, phase, polarity, frequency and waveform from the firsttransmitter signal. The waveform of either the first or secondtransmitter signals may be one of a square waveform, triangularwaveform, sawtooth waveform, sinusoidal waveform, or the like.Furthermore, the length of the in blanking period may be adjusted toaccommodate frequency hopping. That is, the ratio of time used in adisplay frame between in-frame blanking periods and display updating maychange in order to switch to different transmitter signals. In oneembodiment, in an in-frame blanking period needs to be lengthened toswitch to a transmitter signal with a different frequency, theprocessing system may move the blanking period to a subsequent frame topreserve a minimum display screen refresh rate.

In one embodiment, receiver electrodes may be configured to receiveresulting interference signals during at least a portion of an in-frameblanking period. During this time, the common electrode(s) may befloating or tied to a specific DC voltage. These interference signalsmay then be used to determine which transmitter signal (i.e., whichfrequency) to transmit. The transmitter signal is selected based on theresulting interference signal such that interference may be reduced.

FIGS. 7A-7C are timing charts for processing a display frame withinterleaved capacitive sensing periods, according to embodimentsdisclosed herein. Specifically, FIG. 7A illustrates a timing chart 701for a first display frame. Similar to the timing chart in FIG. 5, chart701 includes multiple display line update periods 305, each including apixel update period 310 and a horizontal blanking period 315, grouped toform multiple display update clusters 505. These clusters 505 areinterleaved with a plurality of capacitive sensing periods 320. Theduration of the clusters 505 may be related or unrelated with theduration of the capacitive sensing periods 320. For example, the inputdevice may set the duration of the clusters 505 and the capacitivesensing periods 320 (by adjusting the vertical or horizontal blankingperiods) based on a predefined ratio. Alternatively, the duration of thecapacitive sensing periods 320 may be independently set without regardsto the duration of the clusters 505 or based solely on mitigating noisethat may occur from performing non-contiguous capacitive sensing.

The display screen is updated based on the display frame by updating thedisplay lines during the display update clusters 505A-D. However, thedriver module pauses updating the display after each cluster 505A-C toperform capacitance sensing during the capacitive sensing periods320A-C. For example, the input device may update the pixels associatedwith the electrodes in the display update cluster 505A and then performcapacitance sensing on those same electrodes during capacitive sensingperiod 320A. Alternatively, the driver module may perform capacitancesensing on at least one electrode that was not updated in the previousdisplay update cluster 505. To reduce interference, in one embodimentthe driver module performs capacitance sensing on electrodes on adifferent portion of the display screen from the display lines that wererecently updated. This may avoid electrical interference (capacitances,inductances, and the like) that temporarily affect the common electrodeseven after updating the display is paused and capacitance sensing hasbegun.

FIG. 7B-7C illustrate two different embodiments of timing charts 702,703 for updating a display screen based on a second display frame thatwas received after the first display frame shown in FIG. 7A. That is,FIGS. 7B and 7C illustrate that the timing chart may change for eachsubsequent frame. In one embodiment, visual artifacts within a displayimage due to interleaving display updating with capacitive sensing maybe reduced by varying properties of the capacitive sensing period fromdisplay frame to display frame. This variation may be done in a randomor non-random manner.

FIG. 7B illustrates shifting the display update clusters 505E-G andcapacitive sensing periods 320E-H relative to the clusters 505A-D andcapacitive sensing periods 320A-C shown in FIG. 7A. The total durationof the timing charts 701 and 702 is the same, but how that time isdivided into the different periods is altered. For example, instead ofstarting with a display update cluster 505, timing chart 702 moves thevertical blanking period 325 (or only a portion thereof) to thebeginning of the display frame update. As discussed previously, theinput device may perform capacitance sensing during the verticalblanking period 325. The timing between the different display updateclusters 505E-G, however, may remain the same. That is, the duration ofthe capacitive sensing periods 320E-G that separate the display updateclusters 505 is preserved relative to the duration of the capacitivesensing periods 320A-C. Doing so may maintain the timing between thedriver module and a video source that is transmitting the display framesto the driver yet still prevent or remove visual artifacts.

FIG. 7C illustrates that the duration of the individual display updateclusters 505 and capacitive sensing periods 320 may change betweensubsequent frames—i.e., between the first frame shown in FIG. 7A and thesecond frame shown in FIG. 7C. For example, the display update cluster505I starts at the same location in the timing chart 702 as displaycluster 505A in timing chart 701, but the duration of the capacitivesensing period 320I is increased relative to the blanking period 320A.In one embodiment, the added length of capacitive sensing period 320Imay come from shrinking one or more horizontal blanking periods 315, thevertical blanking period 325, or increasing the number of correspondinghorizontal blanking periods 315. Alternatively, as shown in FIG. 7C, theinput device uses only two capacitive sensing periods 320I and 320Jinstead of the three capacitive sensing periods 320A-C shown in timingchart 701. The extra time saved by eliminating one of the in-frameblanking periods may be used to expand one or both of the remainingcapacitive sensing periods 320. Moreover, increasing the blankingperiods 320 inherently increases the time separation between the displayupdate clusters 505. Changing this spacing may aid in preventing orremoving visual artifacts.

The timing chart 703 also illustrates increasing the duration of thedisplay update clusters 505 by eliminating one of the clusters shown inFIG. 7A and adding the extra time to the remaining display updateclusters 505I-K. Here, the duration of cluster 505J is extended to betwice that of the other clusters 505I and 505K. In this manner, theinput device may further rearrange the display update clusters 505I-Krelative to the display update clusters 505A-D used in the previouslydisplay frame.

In addition to mitigating noise relative to input device that performnon-contiguous capacitive sensing, FIGS. 7A-C illustrate differenttechniques for rearranging or altering the display update clusters andcapacitive sensing periods 320 to prevent or remove visual artifacts;however, this disclosure is not limited to only these techniques and mayrely other techniques for preventing visual artifacts. In furtherembodiments, the position of the in-frame blanking periods may varyrandomly from display frame to display frame. Moreover, the commonelectrode that is driven for updating the display before the start of ancapacitive sensing period or the common electrode that is drivenfollowing a capacitive sensing period may change from display frame todisplay frame. Further, the length of a capacitive sensing period 320may vary within a display frame such that all the capacitive sensingperiods of a display frame are not the same length.

FIG. 8 illustrates a method of interleaving periods of capacitancesensing with display updating, according to an embodiment disclosedherein. The method 800 begins at step 805 with a video sourcetransmitting a display frame to a processing system which updates thepixels of a display screen based on the frame data. The video source maytransmit the display frame either as a large chunk—i.e., all the data atone time—or intermittently—i.e., smaller chunks of the display frame aretransmitted at intervals.

At step 810, the driver module of the processing system updates one ormore display lines of the display screen based on the received displayframe data. The driver module may use, for example, a set of electrodeswhich includes common electrodes for generating an electric field thatupdates the pixels in the display screen. During a display line update,the driver module selects at least one common electrode and updates thepixels associated with that electrode. In some embodiments, the displayscreen may associate different color pixels with each common electrode.Thus, the driver module may perform multiple display updates using asingle common electrode—e.g., an update for red, green, and blue pixels.

At step 815, display updating may be paused during an in-frame blankingperiod. In one embodiment, pausing display updating results in thedriver module ceasing to update the pixels in the display screen.Instead of updating the display, at step 820, the driver module (or adifferent circuitry module) may use the common electrodes to performcapacitance sensing. The driver module drives a transmitter signal on atleast one of the common electrodes (or a transmitter electrode). Thetransmitter signal generates a resulting signal on one or more receiverelectrodes. A touch detection module may use the resulting signal toderive positional information for an input object near the touchsensitive area of the input device. In one embodiment, the touchdetection module measures the capacitance or the change of capacitancebetween the common electrode and the receiver electrodes.

In one embodiment, the duration of the capacitive sensing period may beat least as long as the pixel update period or the display line updateperiod. For example, the duration of the capacitive sensing period maybe set according to the number of sensing cycles needed to determine thechange in capacitance for one or more common electrode and the receiverelectrodes. Stated differently, the input device may set the duration ofthe in-frame blanking period such that an accurate measure ofcapacitance for a common electrode may be obtained by transmittingsensing cycles contiguously—i.e., without substantial interruptions. Forexample, if the driver module requires ten sensing cycles to accuratelyobtain a capacitance measurement, the duration of the capacitive sensingperiod is at least long enough to perform the ten cycles.

At step 825, the processing system may resume updating the display.Specifically, the processing system updates additional display linesbased on the display frame data. Moreover, the processing system mayreceive additional portions of the display frame in embodiments wherethe entire display frame is not transmitted at the same time.

An Example Display Device

FIG. 9 illustrates a system for communicating between an electronicsystem and an input device that interleaves capacitive sensing periodswith display updating periods, according to one embodiment disclosedherein. The input device 100 includes an electronic system 150 and adisplay device 101 that includes an integrated sensing device. Asmentioned in regards to FIG. 1, the electronic system 150 broadly refersto any system capable of electronically processing information. Somenon-limiting examples of electronic systems 150 include personalcomputers of all sizes and shapes, such as desktop computers, laptopcomputers, netbook computers, tablets, web browsers, e-book readers, andpersonal digital assistants (PDAs). The electronic system 150 includes agraphics processor 905 that transmits data to the input device 100 fordisplay. Specifically, the graphics processor 905 transmits displayframes to the input device 100, and as such, may be referred to as avideo source. The processor 905 is any suitable processor for generatingdisplay data and may include multiple processors, a multi-coreprocessor, and the like. The graphics processor 905 may be a specializedprocessor for performing graphics processing or a general purposeprocessor.

The input device 100, in one embodiment, may be configured to provideinput to an electronic system 150 as well as receive and process displaydata transmitted from the electronic system 150. The input device 100includes a display screen 930 and a processing system 110. The displayscreen 930 includes a plurality of pixels arranged as one or moredisplay lines that are updated based on display frames received from thegraphics processor 905. The electronic system 150 may include in thedisplay frame built-in periods for the horizontal and vertical blankingperiods. The processing system 110 may alter or redistribute these builtin timing periods to generate the in-frame blanking periods discussedabove. For example, if the display frame designates 100 μs for eachhorizontal blanking period, the processing system 110 may use 90 μs fromeach horizontal blanking period to insert one or more in-frame blankingperiods into the display frame update.

The processing system 110 is configured to operate the hardware of theinput device 100 to detect input in the sensing region—e.g., someportion of the display screen 930. The processing system 110 comprisesparts of or all of one or more integrated circuits (ICs) and/or othercircuitry components. As shown, in one embodiment, the processing system110 includes at least a display driver module 910, a buffer 915, a touchdriver module 920, and a communication interface 925. The communicationinterface is communicatively coupled to the electronic system 150, andmore specifically, to the graphics processor 905 via connection 940. Thecommunication interface 925 receives display frames from the graphicsprocessor 905 which are stored in the buffer 915. However, in someembodiments, the input device may not need temporary storage to storethe received display frame portions (i.e., the frame data is processesas fast as it is received), and thus, the buffer 915 may be omitted. Theinterface 925 may communicate with the electronic system 150 using a oneor more different control signals which will be discussed in furtherdetail below. In one embodiment, the communication interface 925 maytransmit data to and receive data from the electronic system alongconnection 940 using buses, networks, or other wired or wirelessinterconnections.

The processing system 110 may use the buffer 915 to temporary store thedisplay frames received from the graphics processor 905. The buffer 915may be any memory storage element such as a random access memory (RAM),a plurality of bistable latching memory elements, an erasableprogrammable read-only memory (EPROM or Flash memory), and the like.Further, the buffer 915 may be integrated with all the other elements inthe processing system 110 into a single IC or may by located “off chip”and be communicatively coupled to the other components of the processingsystem 110. In yet other embodiments, the buffer 915 may be integratedas part of the electronic system 120 and/or as part of the graphicsprocessor 905. The buffer 915 may be fabricated with enough memorycapacity to store at least one display frame. Stated differently, thebuffer 915 is capable of storing enough data to update each pixel in thedisplay screen 930. As the processing system 110 finishes updating thedisplay screen 930 based on the display buffer, the buffer 915 may becleared or replaced by another display frame transmitted from thegraphics processor 905.

Alternatively, the buffer 915 may have the capacity to store only aportion of the display frame—i.e., only enough data to perform some ofthe display line updates in a display frame. In this embodiment, thegraphics processor 905 may transmit individual chunks of the displayframe to the processing system 110. The graphics processor 905, forexample, may transfer a chunk of the display frame (e.g., datacorresponding to ten display line updates) which is stored in the buffer915, wait for the processing system 110 to update the display based onthe data, and transmit an additional chunk—e.g., ten more displaylines—after the processing system 110 requests additional data. However,this assumes that the connection 940 is able to transmit data fasterthan the processing system 110 can update the display screen 930. Ifnot, the buffer 915 may constantly be swapping out data that has alreadybeen used to update the display 930 with new data received from theelectronic system 150. That is, the connection 940 is constantly sendingdata rather than transmitting data in bursts.

The display driver module 910 may include circuitry which drives thecommon electrodes 935. The processing system 110 may control the displaydriver module 910 such that the display screen 930 is updated based on areceived display frame from the graphics processor 905. That is, thedisplay driver module 910 uses the information stored in the buffer 915to update the pixels in the display screen 930. Although in input device100 the display driver module 910 is connected to only the commonelectrodes, the module 910 may also be coupled to a second correspondingset of electrodes or transistors that are driven in tandem with thecommon electrodes 935 to update the pixels.

The processing system 110 includes a touch driver module 920 forperforming capacitive sensing. The processing system also has theability to switch control of the common electrodes 935 between thedisplay driver module 910 and the touch driver module 920. Althoughshown as two separate elements, the circuitry or the firmware of thedisplay driver module 910 and the circuitry or the firmware of the touchdriver module 920 may be combined into a single element or integratedinto a single processing system IC. Once the processing system 110pauses display updating, the touch driver module 920 drives transmittersignals onto the common electrodes 935 for detecting changes incapacitance between the common electrodes and receiver electrodes (notshown). If the capacitance sensing occurs during an in-frame blankingperiod, once the capacitance sensing (or a portion thereof) is complete,the processing system 110 resumes updating the display screen 930 basedon the received display frame using the display driver module 910.

The processing system 110 and electronic system 150 may use one or morecontrol signals to communicate and regulate how or when the displayframes are transmitted. The display driver 101 may be designed such thatthe connection 940 transmits the display frames to the processing system110 at its fastest data bit rate even if the processing system 110 isunable to update the display at the same rate. Transmitting as much dataas possible may minimize the time the connection 940 is used, therebyextending the battery life of the input device 100.

In one embodiment, the processing system 110 may use a control signal topause the flow of display frame data from the electronic system 150 andthe processing system 110. The electronic system 150 may receive astatus indicator signal from the processing system 110 that includes theamount of data that has been processed from the buffer 915. For example,the processing system 110 may use the status signal to inform theelectronic system 150 how much of the data in the buffer 915 has beenprocessed. For example, if the buffer 915 holds enough data to updatetwenty display lines, the processing system 110 may send an alert usingthe status signal when the 19 display line has been updated. Theelectronic system 150 may use the alert to extrapolate a predicteddisplay frame rate. That is, if the alert arrives at predictableintervals, the electronic system 150 may extrapolate a rate fortransmitting the display frame to the processing system 110—e.g.,transmit twenty lines of the display frame every 100 μs. Thus, even ifthe status signal is no longer transmitted, the electronic system 150may use the extrapolated rate to continue to send updated display data.Alternatively, the electronic system 150 or the processing system 110may be preconfigured to operate at a certain rate, and thus, the statussignal is not necessary.

However, the extrapolated rate may cause an underflow or overflow in thebuffer 915 when display updating is paused to perform capacitancesensing during in-frame blanking periods. For example, FIGS. 7B and 7Cshow rearranging the display update clusters 505 and capacitive sensingperiods 320 in subsequent display frames. Referring to FIG. 7B, becausethe display frame does not start with a display update cluster, theelectronic system 150 may transmit additional frame data using theconnection 940 even though the processing system 110 has not yetprocessed the frame data already in the buffer 915, which may cause anoverflow. Alternatively, referring to FIG. 7C, the display updatecluster 505J has a longer duration than the other clusters 505A-D in thefirst frame. Accordingly, the processing system 110 may still beattempting to update the display screen during display update cluster505J even when the display driver module 910 has exhausted the data inthe buffer 915, resulting in an underflow. Accordingly, the processingsystem 110 and electronic 150 may need to change the extrapolated rateor use a different communication technique to mitigate or prevent bufferunderflows and overflows.

In one embodiment, the processing signal 110 may prevent underflow oroverflows by using the status signal to pause display updating. Forexample, the processing system 110 may include logic for determiningwhen to switch between a display update cluster period and an in-frameblocking period. Once determining to begin capacitance sensing, theprocessing system ceases sending updates in response to the statussignal. In this embodiment, the electronic system 150 does not rely onan extrapolated rate to determine when to send a display frame andinstead transmits a display frame in response to receiving an alert onthe status signal. In one embodiment, the processing system 110 pausesdisplay updating by switching control of the common electrodes 935 tothe touch driver module 920 and ceasing to send updates of the buffer'susage on the status signal. Without receiving updates or alerts, thegraphics processor 905 temporarily stops sending the display frame, orportions thereof, to the processing system 110. Once the processingsystem 110 determines to resume updating the display—i.e., the in-frameblocking period has, or is about to, complete—the status signal maytransmit an alert to the electronic system 150 which responds bytransmitting a portion (or an entire) display frame to the processingsystem 110. Because of latency or other processing time, the processingsystem 110 may instruct the electronic system 150 to begin sending moredisplay frame data before the in-frame blanking period is over to ensurethat the display line updates can begin once the blanking period iscomplete. Note that the processing system 110 may use a different orseparate control signal for instructing the electronic system 150 topause transmitting frame data. For example, the processing system 110could continue to send an update of the buffer's usage using the statussignal but prevent the electronic system 150 from transmitting more databy using a second control signal. Throttling the flow of frame data fromthe electronic system 150 may minimize the size of the buffer 915 evenwhen arrangement and duration of display update clusters and in-frameblocking periods may change between subsequent frames.

In another embodiment, the electronic system 150 may control when topause updating the display—i.e., when to insert an in-frame blankingperiod. For example, the graphics processor 905 may have the necessarylogic for controlling when the processing system 110 switches betweenupdating the display using the display driver module 910 and performingcapacitance sensing using the touch driver module 920. Because in thisembodiment the electronic system 150 controls the arrangement of thedisplay update clusters and in the in-frame blanking periods, the statussignal may not be needed. For example, the processor 905 may bepreconfigured such that the length of time needed for the processingsystem 110 to update a portion of the display frame—e.g., a singledisplay line—and the size of the buffer 915 are stored in memory. Basedon this knowledge, the electronic system 150 may transmit the displayframe as either a single chunk or in intermittent portions to theprocessing system 110 in a manner that prevents the buffer fromexperiencing an underflow or overflow. Moreover, to prevent visualartifacts, the logic of the graphics processor 905 may change thearrangement and/or the duration of the display update clusters and thein-frame blanking periods in the display frame. Based on the chosentechnique for preventing the artifacts, the graphics processor 905 usesa control signal to pause updating the display. That is, the controlsignal instructs the processing system 110 to switch control of thecommon electrodes 935 from the display driver module 910 to the touchdriver module 920.

CONCLUSION

Input devices with display screens periodically update (refresh) thescreen by selectively driving common electrodes corresponding to pixelsin a display line. In general, the input devices drive each electrodeuntil each display line (and each pixel) of a display frame is updated.In addition to updating the display, the input device may performcapacitive sensing using the display screen as a proximity sensing area.To do this, the input device may interleave periods of capacitivesensing between periods of updating the display based on a displayframe. For example, the input device may update the first half ofdisplay lines of the display screen, pause display updating, performcapacitive sensing, and finish updating the rest of the display lines.In this manner, the time period necessary for updating a screen based ona single display frame includes one or more interleaved periods ofcapacitive sensing. Further still, the input device may use commonelectrodes for both updating the display and performing capacitivesensing.

The embodiments and examples set forth herein were presented in order tobest explain the embodiments in accordance with the present technologyand its particular application and to thereby enable those skilled inthe art to make and use the invention. However, those skilled in the artwill recognize that the foregoing description and examples have beenpresented for the purposes of illustration and example only. Thedescription as set forth is not intended to be exhaustive or to limitthe invention to the precise form disclosed.

In view of the foregoing, the scope of the present disclosure isdetermined by the claims that follow.

What is claimed is:
 1. A processing system for a display devicecomprising an integrated capacitive sensing device, the processingsystem comprising: a display driver module comprising driver circuitry,the display driver module configured to be coupled to a plurality ofcommon electrodes configured to be driven for updating a plurality ofdisplay lines in a display screen of the display device and performingcapacitive sensing, wherein the display driver module is configured todrive a first one of the plurality of common electrodes for updating afirst one of the plurality of display lines during a first time periodof a first display frame and drive a second one of the plurality ofcommon electrodes for updating a second one of the plurality of displaylines during a second time period of the first display frame; and atouch driver module configured to drive a first sensor electrode forcapacitive sensing during a third time period of the first displayframe, the first sensor electrode comprising at least one commonelectrode of the plurality of common electrodes, and the third timeperiod being at least as long as the first time period and occurringafter the first time period and before the second time period.
 2. Theprocessing system of claim 1, wherein the first sensor electrodecomprises the first common electrode.
 3. The processing system of claim1, wherein the third time period is longer than the first time period.4. The processing system of claim 1, wherein driving the first sensorelectrode for capacitive sensing during the third time period comprisesdriving the first sensor electrode with a sensing signal comprising aplurality of contiguous sensing cycles.
 5. The processing system ofclaim 1, wherein driving the first sensor electrode for capacitivesensing during the third time period comprises driving the first sensorelectrode for absolute capacitance.
 6. The processing system of claim 1,wherein the first sensor electrode is one of a plurality of sensorelectrodes, and wherein the plurality of sensor electrodes is disposedin an array of rectangles.
 7. The processing system of claim 1, whereindriving the first sensor electrode for capacitive sensing during thethird time period comprises driving the first sensor electrode with atransmitter signal and wherein the processing system further comprises areceiver module coupled to a second sensor electrode, wherein thereceiver module is configured to receive resulting signals with thesecond sensor electrode.
 8. The processing system of claim 1, whereinthe display driver module is further configured to: drive a secondsensor electrode for capacitive sensing during a fourth time period ofthe first display frame, the fourth time period being at least as longas the second time period and occurring after the second time period andbefore all of the plurality of display lines have been updated duringthe first display frame.
 9. The processing system of claim 1, furthercomprising a determination module configured to: determine positionalinformation for an input object based on resulting signals acquired whenthe first sensor electrode is driven for capacitive sensing; and acquirea measurement of interference, wherein the first sensor electrode isdriven during the third time period with a first sensing signal having afirst signal frequency and wherein the touch driver module is furtherconfigured to shift from driving the first sensing signal having thefirst signal frequency to driving a second sensing signal having asecond signal frequency based on the measurement of interference. 10.The processing system of claim 1, wherein the touch driver module isconfigured to: drive the first sensor electrode for capacitive sensingduring a fourth time period of the first display frame, the fourth timeperiod occurring after the second time period and before all of theplurality of display lines have been updated during the first displayframe.
 11. The processing system of claim 1, wherein the touch drivermodule is further configured to: drive a second sensor electrode forcapacitive sensing during the third time period of the first displayframe, the second sensor electrode comprising a second at least one ofthe plurality of common electrodes, and wherein the first sensorelectrode and the second sensor electrode are simultaneously driven. 12.A method for operating a capacitive sensing device, the methodcomprising: driving a first common electrode of a plurality of commonelectrodes for updating, during a first time period, a first displayline of a first display frame; driving a second common electrode of theplurality of common electrodes for updating, during a second timeperiod, a second display line of the first display frame; and driving afirst sensor electrode for capacitive sensing during a third time periodof the first display frame, the first sensor electrode comprising atleast one common electrode of the plurality of common electrodes, andthe third time period being at least as long as the first time periodand occurring after the first time period and before the second timeperiod.
 13. The method of claim 12, wherein the step of driving thefirst sensor electrode further comprises: driving the first sensorelectrode with a sensing signal comprising a plurality of contiguoussensing cycles.
 14. The method of claim 12, wherein driving the firstsensor electrode for capacitive sensing during the third time periodcomprises: driving the first sensor electrode for absolute capacitance.15. The method of claim 12, wherein driving the first sensor electrodefor capacitive sensing during the third time period comprises: drivingthe first sensor electrode with a transmitter signal and wherein themethod further comprises receiving resulting signals with a secondsensor electrode.
 16. The method of claim 12, further comprising:driving the first sensor electrode for capacitive sensing during afourth time period of the first display frame, the fourth time periodoccurring after the second time period and before all display lines havebeen updated during the first display frame.
 17. The method of claim 12,further comprising: driving a second sensor electrode for capacitivesensing during a fourth time period of the first display frame, thefourth time period being at least as long as the second time period andoccurring after the second time period and before all display lines havebeen updated during the first display frame.
 18. A display device havingan integrated capacitive sensing device, the display device comprising:a plurality of common electrodes configured to be driven for updating aplurality of display lines of a display screen of the display device andperforming capacitive sensing; a plurality of receiver electrodes; and aprocessing system coupled to the plurality of common electrodes and tothe plurality of receiver electrodes, wherein the processing system isconfigured to: drive a first one of the plurality of common electrodesfor updating, during a first time period of a first display frame, afirst one of the plurality of display lines and a second commonelectrode of the plurality of common electrodes for updating, during asecond time period of the first display frame, a second one of theplurality of display lines; drive a first sensor electrode forcapacitive sensing during a third time period of the first displayframe, the first sensor electrode comprising at least one commonelectrode of the plurality of common electrodes, and the third timeperiod being at least as long as the first time period and occurringafter the first time period and before the second time period.
 19. Thedisplay device of claim 18, wherein driving the first sensor electrodefor capacitive sensing during the third time period comprises drivingthe first sensor electrode for absolute capacitance.
 20. The displaydevice of claim 18, wherein driving the first sensor electrode forcapacitive sensing during the third time period comprises driving thefirst sensor electrode with a transmitter signal and wherein theprocessing system further comprises receiving resulting signals with asecond sensor electrode.
 21. The display device of claim 18, wherein thefirst sensor electrode is one of a plurality of sensor electrodes andwherein the plurality of sensor electrodes is disposed in an array ofrectangles.